Field of the Invention
The invention relates to a process gas preparation device for an industrial heat treating furnace system. In addition, the invention relates to an industrial heat treating furnace system for gas carburizing and hardening of metal workpieces which includes the aforementioned process gas preparation device.
Description of the Related Art
Industrial furnace systems usually make use of process gases, which serve to protect the surface of the metal workpieces to be treated in the respective industrial furnace and also to change the chemical composition of such workpieces. When hardening metal workpieces, it is known to carburize the workpieces by the use of the process gas. The process gas in such case is usually composed of a protective gas including carbon monoxide, hydrogen, and nitrogen, carbon dioxide, oxygen, and/or water vapor, as constituents, as well as a hydrocarbon enrichment gas for the carburizing process. In a treatment chamber of the respective industrial furnace into which the metal workpiece is introduced for the carburizing process and hardening, an excess pressure is to be generated with the process gas, so as to prevent ambient air from inadvertently entering the furnace chamber. Such condition also guarantees a carbon level in the treatment chamber sufficient for carburization of the metal workpieces.
The treatment chamber of the known industrial heat treating furnace is typically rinsed with process gas, i.e., the process gas is continuously flowed through the treatment chamber. After the process gas flows through the chamber, the gas is routed to a burn-off location of the industrial furnace where the process gas is discharged and then safely ignited by a pilot burner and burned. However, since this results in a correspondingly large consumption of process gas, and corresponding higher emissions also arise in the area of the industrial furnace, there are known systems in which the process gas is regenerated or prepared in a closed loop after flowing through the treatment chamber of the respective industrial furnace. The recycled process gas is subsequently available for renewed supply to the treatment chamber of the industrial furnace.
Known from U.S. Pat. No. 8,333,852 is an industrial furnace system for gas carburizing and hardening of metal workpieces, in which a process gas preparation device is provided in the area of an industrial furnace having a treatment chamber. This process gas preparation device includes a preparation reactor having a catalyst therein. The preparation reactor is connected with the treatment chamber of the furnace system by a gas feed line, so that spent process gas can be conducted out of the treatment chamber and into the preparation reactor. Also provided between the preparation reactor and the treatment chamber of the industrial furnace is a gas return line, which functions to return the process gas from the preparation reactor back into the treatment chamber of the industrial furnace. In this way the furnace treatment chamber and the preparation reactor are connected in a closed loop through the gas feed and return lines. In addition, a hydrocarbon gas and/or air can be supplied to the preparation reactor by respective additional feed lines so as to be able to prepare or regenerate the spent process gas by reaction with the catalyst and provide a desired carbon content. In order to supply the spent process gas to the preparation reactor and return it into the treatment chamber of the industrial furnace, the feed line incorporates a compressor, which is controlled by means of a control device that also regulates process gas preparation and return.
Proceeding from the state of the art as described above, it is an object of the present invention to provide a process gas preparation device for an industrial furnace system, wherein this process gas preparation device is intended to make it possible to configure a preparation of spent process gas and a supply thereof to the industrial furnace as optimally as possible.